Rotor and gear assembly for rotary mechanisms

ABSTRACT

An improved rotor and gear assembly for rotary mechanisms, such as combustion engines or the like, in which the gear is seated in one face of the rotor and secured to the rotor by a plurality of circumferentially spaced fastening means extending from the face of the rotor opposite from the gear, through the rotor, into the gear to thereby flexibly secure the gear against radial movement due to thermal distortion resulting from cyclically varying stress loads and thermal induced stresses.

lJnited tates ater1t Hermes eiit a1.

1151 3,655,32 5] Arm, 1972 54] RQTQR AND GEAR ASE 1111: FOR 3,383,9365/1968 Corwin ..74/433 RUTARY MECHANISMS 3,489,125 1/1970 Fend ..418/61X [72] Inventors: Waiter Hermes, Cedar Grove; Charles OTHER PUBLICATIONSJones Hillsdale both Curtiss-Wright 5 Experimental Rotating CombustionEn- [73] Assignee: Curtiss-Wright Corporation gines by Dr. Max Bentele,Rec d Oct. 1963 (pp. containing 22 Filed: Apr. 2, 1970 F135 27 32 my)[21] App1.No.: 25,220 Primary Examiner-Car1ton R.Croy1e AssistantExaminer-Thomas C. Perry Attorney-Arthur Frederick and Victor D. Behn[52] U.S.Ci ..4l8/61,74/433,418/91 [51] 1111. C1. ..F01c 17/02, F161151/08 57 STRACT [58] i ieidofsearch ..74/432,433;4l8/61,91,92

An 1mproveo rotor and gear assembly for rotary mechanisms, l 56]Reierehms fited such as combustion engines or the like, in which thegear is seated in one face of the rotor and secured to the rotor by aUNITED STATES PATENTS plurality of circumferentially spaced fasteningmeans extending from the face of the rotor opposite from the gear,through 3,176,915 4/1965 Bentele et a1. ..418/91 x the rotor, into thegear to thmhy flexibly Seem the gear 1409604 9/1968 Jones "74/433against radial movement due to thermal distortion resulting 3,206,109 9/1965 Paschke ..418/61 from cyclically varying Stress loads and thermalinduced 3,444,842 5/1969 Bensinger et a1 ..4l8/91 X Stresses. 3,111,88411/1963 Peras ..418/61 3,302,624 2/1967 Tatsutomi ..418/91 X 2 Claims, 6Drawing Figures 6 4% /fl 7L r J ,l a

i -s "11 /5 1 M5 j/ I25 3d Z7 25 f}: 4 v n 4 ,5; /7 1 5 25 Zl /"Z4Q' 3 lll i; f by a $7 ROTOR AND GEAR Asses/mm FOR ROTARY MEtIHANTSh/lS Thisinvention relates to rotary mechanisms for fluid pumps, fluid motors,compressors, combustion engines or the like. More specifically, theinvention relates to a rotor and gear assembly for such rotarymechanisms.

BACKGROUND OF THE INVENTION Heretofore, rotor and gear assemblies of thetype exemplified in the US. Pat. 17 to Jones, No. 3,400,604, whileconstituting an improvement over then known assemblies, were stillsubject to failures resulting from cyclically varying loads andthermally induced stresses imposed upon the rotor and gear assemblies.At least some of the failures were attributable to excessive expansionof the rotor hub portion relative to the timing gear and theconcentration of stress in a sharp shoulder partly defining the seat forthe gear in one face of the rotor. Other failures, in the heretoforeknown rotor and gear assemblies, were the loosening of gear holdingbolts which can be attributed to excessive differential expansion andcontraction between the holding bolts and the rotor. Accordingly, thepresent invention contemplates an improved rotor and gear constructionwherein thermal distortion and resultant stresses in the gear and rotor,which caused the aforementioned failures, are substantially minimized.

It is, therefore, an object of the present invention to provide animproved rotor and gear assembly having a longer operative life thenheretofore known rotor and gear assemblies.

It is another object of this invention to provide an improved rotor andgear assembly of relatively simple construction and yet having a highdegree of reliability as compared with heretofore known rotor and gearassemblies.

It is a further object of this invention to provide an improved rotorand gear assembly capable of operating at high loads and speeds withfailures resulting therefrom substantially minimized.

It is yet another object of this invention to provide an improved rotorand gear assembly wherein each component is of improved construction tocooperatively function to produce an assembly highly resistant tocyclically varying loads and thermal stresses.

A feature of this invention is the attachment of the gear to the rotorby holding means, such as bolts, extending through the rotor, from oneface thereof to engage the pilot bosses of the gear seated in theopposite face of the rotor. The construction provides pilot bosses andribs and holding means, such as bolts, of relatively long dimension in adirection parallel to the axis of the rotor so that a substantial amountof the rotational force imposed by the radial thermal expansion of therotor hub, relative to the gear is absorbed by the flexure and extensionof the holding means, and thus torsional bending stresses on the gearare substantially less than in heretofore known rotor and gearassemblies. This feature also permits the fabrication of the gear sothat toothed body portion has a relatively small radial dimension incross-section for flexibility to absorb the torsional bendingdisplacement imposed by thermal expansion loads and a relatively largecross-sectional dimension in an axial direction for structural strengthand reduced stress and for providing an annular projection to limitaxial movement of the rotor relative to the housing.

Another feature of the present invention is the provision of positioningand arranging the reinforcing ribs of the rotor in circumferentiallyspaced relation to each other and spaced from thinnest cross-sectionalportion of the rotor in a radial direction adjacent the combustionrecess area of the rotor so that each of the ribs has a large depth in aradial direction and a relatively large curved fillet at the rib root.This feature provides ribs of increased strength as well as obviatingpoints of stress concentration and potential failure in the ribs.

SUMMARY OF THE INVENTION The present invention contemplates an improvedrotor and gear assembly for a rotary mechanism, such as pumps, com

pressors, combustion engines, or the like, comprising a rotor having aplurality of apex portions interconnected by a plurality of peripheralwall portions and opposite, substantially parallel, end faces. One endface is provided with a recess to form a seat for a ring shaped gear,such as a timing gear for a rotor of a rotary internal combustion engineof the type disclosed in the U.S. Pat. No. 3,176,915 to Bentele et al.The gear has a plurality of circumferentially spaced piloting bosses andribs which extend parallel to the gear axis and are adapted to contactthe rotor seat. The piloting bosses are disposed equiangularly from eachother and are constructed and arranged to receive a fastening means,such as a bolt or the like. Each of the fastening means extends from therotor end face, opposite from the gear, through the rotor, to engage theassociated piloting boss of the gear and hold the gear to the rotor.Each fastening means and the piloting bosses and ribs are of relativelylong length to coact to provide a firm, yet flexible connection tominimize radial movement of the gear due to thermal distortion resultingfrom cyclically varying loads and thermal induced stresses.

The gear peripherally is adapted to coact with the rotor to provide aseat for an end seal, thus eliminating the need for a conventional oilseal adapter ring and thereby simplifying the rotor-gear assembly whileretaining the annular axial projection for limiting the axial movementof the rotor relative to the housing which feature is disclosed in US.Pat. No. 3,261,542.

The rotor is provided with a plurality of reinforcing ribs which arearranged in circumferentially spaced relation to each other and spacedfrom the thinnest cross-sectional portion of the rotor, in a radialdirection, adjacent the combustion recess area of the rotor so that eachof the ribs has a large depth in a radial direction and a relativelylarge curved fillet portion at the rib root. This construction providesribs of increased structural strength, as well as obviating points ofstress concentration and potential failure in the ribs. The outerperipheral surfaces of the pilot bosses and ribs of the ring gear areeach chamfered toward the rotor axis to further provide rotorreinforcing ribs, particularly those rotor ribs adjacent theaforementioned thinnest cross-sectional portion of the rotor, ofrelatively large depth.

Also to obviate a loosening or failure of the fastening means, thebosses of the rotor for receiving the fastening means are offset fromthe rotor reinforcing ribs so that the thermal loads to which theperipheral surface of the rotor is exposed is not as readily transmittedto the rotor bosses, through the ribs, as in heretofore known rotor-gearassemblies, so that the torsional bending stress in the gear and thethermal load on the fastening means which tends to radially shift theposition of the rotor and gear bosses relative to the fastening means issubstantially minimized.

BRIEF DESCRIPTION OF DRAWING The invention will be more fully understoodfrom the following description when considered in connection with theaccompanying drawings in which:

FIG. 1 is an elevational view of the end face of the rotor and gearassembly, opposite from the end face to which the gear is secured;

FIG. 2 is a vertical sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is a fragmentary view in cross-section taken along line 33 ofFIG. 1;

FIG. 4 is a fragmentary cross-sectional view taken substantially alongline 44 in FIG. 2, with parts broken away for illustration purposes andon a somewhat enlarged scale;

FIG. 5 is a cross-sectional view taken along line 55 of FIG. 4; and

FIG. 6 is a fragmentary view in cross-section taken along line 6-6 ofFIG. 4 and shown on a somewhat reduced scale.

DESCRlPTlON OF THE PREFERRED EMBODIMENT Now referring to the drawing,the reference number 10 generally designates the rotor and gearassembly, according to this invention, which assembly is suitable for arotary mechanism, such as fluid pumps, compressors, fluid motors, andparticularly applicable to rotary, internal combustion engines. Therotor and gear assembly 10 comprises a rotor 11 and a gear 12. In aninternal combustion engine application of rotor and gear assembly 10,gear 12 is a timing gear which meshes with a pinion gear (not shown)mounted on an eccentric shaft (not shown).

The rotor 11 may be, as shown in FIG. 1, a unitary, cast body ofrelatively soft metal having a substantially triangular profile formedby three spaced apex portions 13 interconnected by arcuate shapedperipheral wall portions 14. As shown in FIG. 2, the rotor body has twoopposite end faces 15 and 16 and an integral recessed hub portion 17.Hub portion 17 is joined to the peripheral wall portions 14 by acircumferential web 18 lying in a plane substantially normal to therotor axis and juxtaposed, circumferentially spaced ribs 19 extendingfrom opposite sides of web 18 to end faces 15 and 16 in planessubstantially normal to the web. The hub portion 17 has a bore lined bysuitable bearing material 21) through which the eccentric of the shaft(not shown) extends to support the rotor for rotation in a substantiallyepitrochoidal shaped chamber (not shown). An apex seal 21 is mounted ineach apex portion 13 to engage the walls (not shown) of the chamber (notshown) in which the rotor rotates to define a plurality ofvolumetrically variable working chambers (not shown). To provide anadequate volume for combustion in the working chambers in the case of aninternal combustion engine, each of the surfaces of peripheral edgeportions 14 are recessed at 22 to form combustion pockets. The hubportion 17 in end face 16 is recessed to receive gear 12 and is providedwith an internal annular notch 23 against which gear 12 abuts or seats.Due to the cyclically varying loads imposed on the rotor due, forexample, in the case of a rotary internal combustion engine, by thecompression and combustion occurring in the working chamber adjacenteach combustion pocket recess 22 of the rotor, as well as the thermaldistortion imposed on the rotor and gear due to thermal gradients anddifferential expansion and contraction between rotor 11 and gear 12, therotor and gear assembly 10 must be constructed and interconnected toprovide a tight or firm, yet flexible, attachment of the gear to therotor. To this end, an improved fastening means, rotor and gearconstruction, according to this invention, is provided.

Gear 12 is provided with a plurality of circumferentially spaced bosses24a and rib portions 2 projecting from internal toothed portion 25 inparallelism to the axis of the gear. The bosses 24a, preferably threebosses equiangularly arranged as shown in Fit}. 1, are each arcuateshaped enlargements and have a tapped hole 26 therein to engage afastening means, such as a bolt 27 (see H68. 2, 4 and 5) having athreaded shank portion 28 which is receivable in the tapped hole 26.Each of the bolts 27 extends through a bore 29 in a rotor boss 31)formed in hub portion 17 of side face 15, which bore 29 is in alignmentwith tapped hole 26 in pilot boss portions 240. Boss 30 may include, asshown in FIGS. 2 and i, a partial boss on the gear side of web 18. Sincethe tapped holes 26 are formed in gear 12 of hardened metal, rather thanas heretofore in the relatively soft rotor body, the strength of theconnection between the gear and the rotor is considerably improved. Eachof the bores 29 is counterbored at 31 to provide an annular shoulderagainst which the head portion 32 of bolt 27 abuts. The shank of eachbolt 27 is of reduced diameter in relation to the diameter of bore 29 toprovide a relatively elastic shank and one which can undergo flexurerelative to hub portion 17 of the rotor. A pin type key 33 is employedto lock each of the bolts against rotation relative to the rotor.

Since each of the bolts 27 is dimensioned to extend from the hub portion17 of face 15 substantially the entire width of the hub portion, thebolt has a relatively long shank of substantially greater flexibilitythan heretofore known gear holding bolts. The gear bosses 24a and ribs24 are also relatively long, the bosses, ribs and bolts 27 coacting tominimize the transmittal of rotative force or rotational deformation, ofthe gear about its centroidal axis, from the rotor hub portion 17 togear 12 due to differential expansion and contraction between the hubportion 17 and gear 12. Thus, the stresses on gear 12 and the potentialfailure of the gear are substantially less than in conventionalrotor-gear assemblies.

The peripheral toothed portion 25 of gear 12 is of relatively largedimension in an axial direction since it need not be recessed to provideroom for a conventional end seal adapter (not shown). Thus, the gear isprovided with added structural strength and such added body also permitsfabrication of an annular stepped notch 34 which defines with theadjacent peripheral rotor surface a grooved retaining seat for an endring seal (not shown). In addition, the toothed portion 25 has anannular, axially projecting surface 2511 which lies in a plane outwardlyof the rotor surface 16 to limit axial movement of rotor 11 in the rotorhousing (not shown). Thus, the rotor and gear assembly 10 obviates theneed for an end seal adapter ring and thereby provides the assembly withgreater reliability while simultaneously retaining the annular, axiallyprojecting surface for limiting axial movement of the rotor relative toits housing. A similar annular stepped notch 34a is provided in theopposite end face 13 of rotor 11 to also receive another end seal ring(not shown).

The gear 12, as in conventional rotor-gear assemblies, is dimensioned inrelation to the recess in end face 16 to be spaced along its outerperipheral surface from the ribs 19 of the rotor so that the necessityfor accurate machining of the distal ribs surfaces is obviated. Also,the inner surface of the gear is dimensioned to loosely seat withinnotch 23 so that, upon heating and the differential expansion betweenthe rotor and gear, the gear and the surfaces of notch 23 only then comeinto tight abutment. This latter mentioned cool-loose fit, minimizes thestresses imposed on the gear and rotor due to the thermal loads to whichthe assembly is subjected.

Also, as is conventional and as shown in FIGS. 4, 5 and 6, a pilot pin35 is disposed in aligned bores in each gear boss 24a and a blind" holein boss 30 of the rotor. The pins 35 function to restrain relativemovement of rotor 11 and gear 12 in planes perpendicular to the rotorand gear axes.

Another improved feature of rotor and gear assembly 10 is, as best shownin FIG. 3, forming of the gear bosses 24a and ribs 24 so that the distalsurfaces 36 of bosses 24a and ribs 24 have a relatively steeply inclinedchamfer which permits the adjacent ribs 19 to have a relatively largedimension depth, X and, hence, sufficient structural strength tominimize fracture thereof. To provide sufficient rib body for requisitestructural strength is of particular importance to the ribs 19, nextadjacent to the thinnest cross-sectional part of rotor 11 between hubportion 17 and peripheral walls 14. These ribs 19, hereinafterdesignated by the letter R, are offset from the thinnest cross-sectionalpart of the rotor, which offset location permits the ribs to have agreater depth than if located at the thinnest cross-sectional part ofthe rotor as is the case of heretofore known rotor-gear assemblies asexemplified in US. Pat. No. 3,400,604. Thus, the offset location of ribsR and the relatively steep chamfered surfaces 36 of the gear coact topermit ribs R to have a depth X and, thus, the desired strength tominimize fracture thereof.

A further improved feature according to this invention relating to ribs19 is that the ribs w are provided at their roots with a relativelylarge radii curvature 37 (see H6. 3) forming a fillet which is free ofpoints of stress concentration which formally existed in heretoforeknown rotor-gear assemblies wherein a sharp corner was proved in theribs to accommodate the bosses and ribs of the gear.

A still further feature of the rotor and gear assembly 10 is that thebosses 24a of the gear and the rotor bosses 30 are offset from ribs 19so that the thermal loads to which the peripheral walls 14 of rotor 11are exposed during compression and combustion of gaseous fluids in theworking chambers (not shown) is not directly transmitted to the bosses24a and 30 through the ribs from the peripheral walls 14 and therebyminimizes misalignment of the bosses and the resultant load and stressesimposed on bolts 27 and pins 35.

It is believed now readily apparent that the improved rotor and gearassembly according to this invention has increased resistance tocyclically variable loads and thermal detorsional stresses and,therefore, longer operative life. It is an assembly which is ofsimplified construction wherein a need for seal ring adapter has beeneliminated to thus provide an assembly of increased reliability.

What is claimed is:

l. A rotor and gear assembly for rotary mechanisms comprising:

a. a rotor having opposite end faces, contiguous peripheral walls and ahub portion formed in a recess in each of the end faces;

b. said hub portion, said peripheral walls and end faces beinginterconnected by circumferentially spaced ribs;

c. each of said ribs being joined to the end faces, hub portion, andperipheral walls and having an inner distal edge portion inclined toextend from said end faces inwardly in a direction toward the hubportion of the rotor;

d. a ring gear having an internal toothed portion and a plurality ofcircumferentially spaced elongated boss portions projecting axially fromthe plane of the toothed portion;

e. each of which has an inner surface extending substantially parallelto the gear axis and a chamfered outer surface extending inwardly towardthe gear axis;

f. said ring gear being disposed to abut said hub portion adjacent saidinner surfaces of said boss portions and with the chamfered outersurfaces of said boss portions closely spaced from the distal inclinededge portions of the circumferentially spaced ribs of the rotor; and

g. fastening means including an elongated, relatively flexible bodyportion for each of said boss portions;

h. a bore in said hub portion for each boss portion coaxially alignedwith the associated boss portion and of a dimension to receive the bodyportion of the fastening means therethrough in spaced relation to thewalls of the bore to permit flexure of the body portion;

i. each of said fastening means extending, from the hub por tion surfaceopposite from the ring gear, through the hub portion to a connection atthe end of the body portion to said boss portion of the gear wherebysaid fastening means and said associated boss portion coact to flexiblysecure said gear against radial movement due to cyclically varying loadsand circumferential distortion from thermally induced stresses.

2. The assembly of claim 1 wherein said fastening means is a bolt havingan elongated flexible shank having a threaded end portion receivable ina threaded hole in each boss portion.

1. A rotor and gear assembly for rotary mechanisms comprising: a. arotor having opposite end faces, contiguous peripheral walls and a hubportion formed in a recess in each of the end faces; b. said hubportion, said peripheral walls and end faces being interconnected bycircumferentially spaced ribs; c. each of said ribs being joined to theend faces, hub portion, and peripheral walls and having an inner distaledge portion inclined to extend from said end faces inwardly in adirection toward the hub portion of the rotor; d. a ring gear having aninternal toothed portion and a plurality of circumferentially spacedelongated boss portions projecting axially from the plane of the toothedportion; e. each of which has an inner surface extending substantiallyparallel to the gear axis and a chamfered outer surface extendinginwardly toward the gear axis; f. said ring gear being disposed to abutsaid hub portion adjacent said inner surfaces of said boss portions andwith the chamfered outer surfaces of said boss portions closely spacedfrom the distal inclined edge portions of the circumferentially spacedribs of thE rotor; and g. fastening means including an elongated,relatively flexible body portion for each of said boss portions; h. abore in said hub portion for each boss portion coaxially aligned withthe associated boss portion and of a dimension to receive the bodyportion of the fastening means therethrough in spaced relation to thewalls of the bore to permit flexure of the body portion; i. each of saidfastening means extending, from the hub portion surface opposite fromthe ring gear, through the hub portion to a connection at the end of thebody portion to said boss portion of the gear whereby said fasteningmeans and said associated boss portion coact to flexibly secure saidgear against radial movement due to cyclically varying loads andcircumferential distortion from thermally induced stresses.
 2. Theassembly of claim 1 wherein said fastening means is a bolt having anelongated flexible shank having a threaded end portion receivable in athreaded hole in each boss portion.